With the advance of aging society, improvement and betterment of living conditions for the aged have been reconsidered, so that attention has been focused on the prevention and treatment of diseases which have so far been disregarded as diseases (e.g., sexual disorders and the like).
Though the role of the 5-HT.sub.2C receptor which is mainly distributed in the central nerve has not been sufficiently revealed, it is considered that this receptor is related to the central nervous system diseases such as sexual disorders, eating disorders, anxiety, depression and sleeping disorders (Curr. Opin. Invest. Drugs, 2 (4), 317 (1993)). In consequence, it is believed that the 5-HT.sub.2C receptor ligand is effective for the prevention or treatment of the aforementioned diseases, particularly diseases which have so far been disregarded as diseases and have no effective therapeutic method (e.g., sexual disorders and the like).
Regarding tricyclic pyrrole or pyrazole derivatives which are 5-HT.sub.2C receptor ligands, a tricyclic pyrrole derivative fused with a benzene ring (EP 657426-A), a tricyclic pyrazole derivative fused with a benzene ring (EP 700905-A) and the like have been reported.
In addition, a tricyclic pyrrole or pyrazole derivative which is fused with a pyrazine ring, a pyridine ring, a thiophene ring, a furan ring or a pyrrole ring is reported as a retinoid antagonist in International Publication WO 96/13478, and a compound having a tricyclic pyrrole or pyrazole nucleus which is fused with an aromatic heterocyclic ring and also has a substituent on a carbon atom of the pyrrole or pyrazole ring in said nucleus is reported as a dopamine receptor ligand in International Publication WO 95/07893.